#!/usr/bin/env python3
# -*- coding: utf-8-*-
import numpy as np
if __name__ == '__main__':
    n = int(input())
    v = np.array(list(map(int, input().split(" "))))
    a = np.zeros((n+1))
    b = np.zeros((n+1))
    for i in range(n):
        a[i+1] = b[i] + v[i]
        b[i+1] = max(a[i], b[i])
    print(int(max(a[n], b[n])))